Create a new vapoursynth.Core every time you reload a script

vspreview/cores.py

@@ -0,0 +1,35 @@
+from vapoursynth import EnvironmentPolicyAPI, register_policy
+from vapoursynth import EnvironmentData
+
+
+__all__ = ("create_and_register_policy",)
+
+
+class VSPreviewEnvironmentPolicy:
+    _current_environment: EnvironmentData
+    _api: EnvironmentPolicyAPI
+
+    def reload_core(self):
+        old_environment = self._current_environment
+        self._current_environment = self._api.create_environment()
+        self._api.destroy_environment(old_environment)
+
+    def on_policy_registered(self, special_api: EnvironmentPolicyAPI):
+        self._current_environment = special_api.create_environment()
+        self._api = special_api
+
+    def on_policy_cleared(self):
+        pass
+
+    def get_current_environment(self) -> EnvironmentData:
+        return self._current_environment
+
+    def set_environment(self, environment) -> EnvironmentData:
+        if environment != self._current_environment:
+            raise ValueError("The passed environment is not valid.")
+
+
+def create_and_register_policy() -> VSPreviewEnvironmentPolicy:
+    policy = VSPreviewEnvironmentPolicy()
+    register_policy(policy)
+    return policy

vspreview/main.py

@@ -1,5 +1,13 @@
 from __future__ import annotations
 
+# import vspreview.cores as early as possible:
+# This is so other modules cannot accidentally
+# use and lock us into a different policy.
+from vspreview.cores import create_and_register_policy
+policy = create_and_register_policy()
+
+# And now back to our regular programing:
+
 import logging
 import os
 from   pathlib  import Path
@@ -9,6 +17,7 @@
 from   PyQt5       import Qt
 import vapoursynth as     vs
 
+
 from vspreview.core import (
     AbstractMainWindow, AbstractToolbar, AbstractToolbars,
     Frame, FrameInterval, Output, Time, TimeInterval,
@@ -608,6 +617,8 @@ def reload_script(self) -> None:
         vs.clear_outputs()
         self.graphics_scene.clear()
         self.outputs.clear()
+        policy.reload_core()
+
         # make sure old filter graph is freed
         gc.collect()